1. Field of the Invention
This invention relates to an air-driven, infinitely variable, pneumatic pulsatile pump for discharging working fluid and, more particularly, relates to a pneumatic pulsatile pump which employs at least two pneumatically independent pumping bladders and a unique pneumatic control circuit which, among other things, permits convenient adjustment from a sharply pulsed flow to a continuously smooth flow through a simple manual adjustment by the user during operation of the pump.
2. Description of the Prior Art
There exist serious shortcomings in the field of fluid pumps, both of the pulsating type and of the smooth-flow (continuous) type. One of the major disadvantages inherent in state of the art pumps is the inability of the user of such pump to vary the flow rates, pressures, and pulsation frequency of the discharging, or working, fluid among a virtually infinite number of settings within a predetermined and controllable range of discharge flow conditions. One area in which this problem is particularly acutely felt is in the surgical field of procedures such as laparoscopy, in orthopedic procedures, and also procedures such as open surgery where a pressurized irrigation fluid is directed through a probe onto the operative surgical site and field to effect removal and debridement of a target tissue and debris. Alternating use of irrigation and suction and simultaneous use of suction and irrigation effects removal of the infused working fluid endogenous to the operative field, and any tissue, blood, char, or debris that has been hydraulically displaced. If the laparoscopist can select the pressure and control the pulse frequency of the working fluid to within close or exact tolerances, the quality of the procedure will be enhanced via these advantages and also through the utilization of the force of the fluid to hydro-dissect tissue planes which separate organs and structures in the body by dissecting these plains via the fluid displacing them at their path of least resistance.
Recent advances in laparoscopic surgical techniques have been numerous. Laparoscopy has now become the procedure of choice for many surgical procedures, and specifically, has become the norm for the removal of the diseased gallbladder (cholecystectomy). Initially, the instrumentation for laparoscopic procedures was archaic and makeshift, borrowed from previously developed gynecological laparoscopic procedures. Recently there have been significant improvements in this instrumentation due to its unprecedented surgical acceptance. One of the recent advancements involves equipment designed for the aspiration and irrigation of working fluid.
The various uses for aspiration and irrigation of fluid include dissection of tissue plains and structures using aqueous solutions, aspiration, rinsing/lavage for enhanced visualization of the surgical site, suction-retraction, blunt dissection, blood clot, tissue removal and debridement, gallstone extraction, and the evacuation of smoke. This diversification of needs makes it imperative that a suction/irrigation system be versatile enough to accomplish any and all tasks.
Of the pulsating irrigation systems presently in use, one such device is disclosed in U.S. Pat. No. 4,741,678 to Nehring, which utilizes a single bladder chamber and, consequently, a limited pulse frequency adjustment. Since only one pump chamber is employed, this pump operates in only a limited range of outputs. In addition, the Nehring device does not incorporate an automatic means for relieving the pressure in the discharge media when flow is terminated. That is to say, when the point-of-use instrument, e.g. laparoscopy probe, is placed in a non-flow state, the discharge media on the upstream side of the instrument remains at an elevated pressure. Since it is desired that no accidental leakage be permitted to occur in most settings where irrigation is performed, the pressurized condition of the discharge media is undesired. None of the pumps heretofore employed have means for virtually instantaneously terminating the flow through the point-of-use instrument while simultaneously reducing the pressure of the discharge media to near ambient.
A representative example of an electrically operated pump is disclosed in U.S. Pat. No. 4,650,462 to DeSatnick et al., which discloses a single source irrigation system. Reliance on electrical energy is undesirable for a variety of reasons, among them, introducing an electrical pumping device in the environment of an operating room and reliance of electronic circuitry and feedback to control and monitor pressures, flows, pulsations, and on/off sensing; the danger of introducing electrical potential in an environment where pure oxygen is present; and the incompatibility of electrical power supplies and required approvals in different countries.
Yet another example of a pneumatic pump is the CODIP tubular diaphragm sold by Warrender, Ltd., Northbrook, Ill., which utilizes a single cylindrical diaphragm and pump housing. This device likewise does not utilize more than one pumping diaphragm and, hence, cannot provide a smooth flow if desired. None of these or any other systems known to the inventors provide a plurality of commonly controlled pneumatically independent pumping bladders which allow for virtually infinite variation of fluid flow pressure and pulse frequency.
Other fluid pumps used in surgical applications such as laparoscopy have relied on saline bottles as a fluid supply reservoir which are pressurized with compressed gas to create flow. Bottles, however, are either not equipped with or rely on floating check valves which may be prone to intermittent or total failure. Failure of these check valves can have negative safety consequences should gas suddenly be emitted from the pump discharge into the patient's abdominal cavity.
A need exists in the field of pulsatile pumps for an easy-to-use, reliable, and versatile pump, the output of which can be infinitely varied between wide limits, with both pressure and pulse frequency independently variable, and which also can produce continuous flows and incorporates a discharge media venting means and user-friendly controls. The instant invention has been developed primarily, though not exclusively, with a view toward achieving the aim of creating a device of the above type with which a user can perform a dynamic range of fluid flow control and irrigation operation in a safe and secure manner.